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Apache Spark 4 | Comparison with previous version
Discover the core differences between Apache Spark 4.0 and Spark 3.x, including performance improvements, columnar execution, streaming upgrades, and Python UDF enhancements.

Apache Spark 4.0 represents a significant evolutionary leap from Spark 3.0, introducing fundamental changes that enhance performance, reliability, and developer experience. This article examines the key technical differences between these major versions, providing insights for engineers planning upgrades and architectural decisions.
Release Overview and Community Impact
Apache Spark 4.0 marks the inaugural release in the 4.x series, representing a major milestone with over 5,100 resolved tickets and contributions from more than 390 developers. This collaborative effort has resulted in substantial improvements across all core components of the Spark ecosystem.
In contrast, Spark 3.0, released in June 2020, focused primarily on performance optimizations, achieving roughly 2x performance improvements over Spark 2.4 in TPC-DS benchmarks, and significantly enhanced Python functionality.
Core Language and Runtime Changes
ANSI SQL Compliance by Default
Spark 4.0 Enhancement: One of the most significant changes in Spark 4.0 is making ANSI mode the default behavior. The spark.sql.ansi.enabled
configuration is now set to true
by default, fundamentally changing how Spark handles SQL operations.
Technical Implications:
- Runtime exceptions are thrown for invalid SQL operations instead of returning null results
- Stricter type checking and data validation
- Enhanced data quality assurance through rejection of invalid casts during table insertions
- Better alignment with standard SQL behavior, improving portability from traditional databases
Spark 3.0 Behavior: Spark 3.0 maintained Hive-compatible behavior by default, often returning null values for invalid operations rather than failing fast with exceptions.
Java Runtime Modernization
Spark 4.0:
- Java 17 as default runtime with Java 21 support added
- Modern JVM features and performance optimizations
- Enhanced garbage collection and memory management capabilities
Spark 3.0:
- Primarily supported Java 8 and 11
- Limited access to modern JVM performance features
- More conservative memory management approaches
Data Type System Enhancements
VARIANT Data Type Introduction
Spark 4.0 Innovation: The introduction of the VARIANT data type represents a major advancement for handling semi-structured data, particularly JSON. This native data type provides:
- Efficient storage and processing of JSON documents without schema definition
- Native JSON operations and querying capabilities
- Better performance for semi-structured data workloads compared to string-based JSON handling
- Seamless integration with SQL and DataFrame APIs
Spark 3.0 Limitation: Semi-structured data handling relied primarily on string manipulation and complex parsing operations, leading to performance bottlenecks and more complex code patterns.
String Collation Support
Spark 4.0 introduces comprehensive string collation support, enabling:
- Locale-specific string comparisons and sorting
- Case-insensitive operations with proper internationalization support
- Enhanced text processing capabilities for global applications
Python Ecosystem Advancements
Python Data Sources
Spark 4.0 Feature: Native Python data source capabilities allow developers to create custom data sources entirely in Python, providing:
- Simplified integration with Python-native data systems
- Reduced barrier to entry for Python developers
- Better ecosystem integration with Python data tools
Polymorphic Python UDTFs
Advanced Function Capabilities: Spark 4.0 introduces polymorphic User-Defined Table Functions (UDTFs) in Python, enabling:
- Functions that can accept varying input schemas
- More flexible data transformation patterns
- Enhanced code reusability across different data structures
Spark 3.0 Baseline: While Spark 3.0 significantly improved Python support with pandas UDF redesign and Python type hints, it lacked these advanced polymorphic capabilities.
Connectivity and Client Architecture
Spark Connect Evolution
Spark 4.0 Improvements:
- Lightweight Python client (pyspark-client) at just 1.5 MB, dramatically reducing deployment footprint
- Additional release tarball with Spark Connect enabled by default
- Full API compatibility for Java clients
- Enhanced remote connectivity patterns
Architectural Impact: These improvements enable better deployment flexibility, reduced container sizes, and simplified client-server architectures for distributed Spark applications.
Spark 3.0 Foundation: Spark 3.0 introduced the initial Spark Connect framework but with larger client footprints and more limited language support.
Streaming and State Management
Streaming State Store Data Source
Spark 4.0 Innovation: Introduction of streaming state store as a data source provides:
- Direct access to streaming state for debugging and monitoring
- Better observability into streaming application state
- Enhanced troubleshooting capabilities for complex streaming pipelines
Operational Benefits:
- Simplified state inspection during development
- Better production monitoring and alerting capabilities
- Reduced debugging complexity for stateful streaming applications
Observability and Debugging Enhancements
Structured Logging
Spark 4.0 Feature: Implementation of structured JSON logging provides:
- Machine-readable log formats for automated processing
- Better integration with modern logging aggregation systems
- Enhanced debugging and monitoring capabilities
- Improved troubleshooting workflows
Production Impact:
- Simplified log analysis and alerting
- Better integration with observability platforms
- Enhanced debugging efficiency for production issues
Performance and Optimization Considerations
Memory Management
Spark 4.0 Advantages:
- Optimizations leveraging Java 17's improved garbage collection
- Better memory utilization patterns with modern JVM features
- Enhanced performance for workloads with complex data types
Spark 3.0 Performance: While Spark 3.0 achieved significant performance gains (2x improvement in TPC-DS benchmarks), it was limited by older JVM constraints and less efficient handling of semi-structured data.
Query Optimization
The VARIANT data type and improved ANSI compliance in Spark 4.0 enable more efficient query plans for mixed structured and semi-structured workloads, particularly beneficial for data lake architectures.
Migration Considerations
Breaking Changes
ANSI Mode Default: The most significant migration consideration is the default ANSI mode behavior. Applications that previously relied on Hive-compatible null-handling behavior may require code modifications.
Java Version Requirements: Applications must be compatible with Java 17 as the default runtime, though Java 8 and 11 remain supported for transition periods.
Compatibility Strategy
Recommended Approach:
- Test existing applications with ANSI mode enabled in Spark 3.x environments
- Validate Java 17 compatibility for all dependencies
- Update error handling logic to accommodate stricter ANSI compliance
- Plan gradual adoption of new features like VARIANT data types
Ecosystem Integration Impact
Data Lake Architecture
Spark 4.0's VARIANT data type and improved JSON handling make it significantly more suitable for modern data lake architectures where semi-structured data is prevalent. This reduces the complexity of ETL pipelines and improves query performance.
Cloud-Native Deployments
The lightweight Python client and enhanced Spark Connect capabilities make Spark 4.0 more suitable for containerized and serverless deployment patterns, aligning with modern cloud-native architectures.
Future-Proofing Considerations
Technology Alignment
Spark 4.0's adoption of modern Java versions, structured logging, and enhanced connectivity patterns positions it well for integration with emerging data technologies and cloud services.
Development Velocity
The improved Python capabilities and enhanced debugging features in Spark 4.0 can significantly accelerate development cycles, particularly for teams working with complex data transformation pipelines.
Conclusion
Apache Spark 4.0 represents a substantial advancement over Spark 3.0, with changes that impact fundamental behavior patterns, performance characteristics, and development workflows. The default ANSI compliance, modern Java runtime, VARIANT data type, and enhanced connectivity features make it a compelling upgrade for organizations seeking improved reliability, performance, and developer productivity.
The migration from Spark 3.0 to 4.0 requires careful planning due to breaking changes, particularly around ANSI mode behavior, but the benefits in terms of data quality, performance, and developer experience make it a worthwhile investment for most organizations. The enhanced support for semi-structured data and improved observability features position Spark 4.0 as a robust platform for modern data architecture patterns.
For technical teams considering the upgrade, the key success factors include thorough testing of existing applications with ANSI mode enabled, validation of Java 17 compatibility, and strategic adoption of new features like VARIANT data types to maximize the value of the migration effort.